Why That Story About a Baby Born to Three Parents Might Be Giving You Déjà Vu

You probably saw the news Tuesday that the world's first baby with DNA from three parents was born earlier this year. You may also have seen people debunking this claim, because there are dozens of people who have been born with the DNA of three people.

So, which is it: a major milestone in genetics or just hype over technology we've had since the 90s? The answer, annoyingly, is a bit of both.

Here's what happened: on Tuesday, New Scientist broke the news that a paper has been submitted to the journal Fertility and Sterility describing the first live birth using a technique called mitochondrial transfer. The parents are a couple from Jordan who had suffered two miscarriages because the mother carries the genes for Leigh syndrome, a severe condition that hinders a fetus's neurological development. But the genes that can cause Leigh syndrome all live in the mitochondrial DNA, or mtDNA, which are separate from the rest of our genes that reside in the chromosomes.

For this procedure, the couple travelled to Mexico, where a team of US doctors injected the nucleus from one of the mother's eggs into a donor egg (which had the nucleus removed). That egg carried the nuclear DNA of the mother, but swapped out her mtDNA for that of the healthy donor. The egg was fertilized by the father's sperm, implanted in the mother, and nine months later you have a healthy baby with no Leigh syndrome and, technically, three parents.

But babies with three parents have been born before, though the process was slightly different. In the past, a handful of infertile couples have been able to conceive by having the mother's egg injected with cytoplasm—the "goo" the holds the nucleus and the mitochondria together in a cell—from a healthy donor. Usually, the cytoplasm could have some mitochondria in it, which meant the baby would have the DNA of three people.

What's different here is that the mitochondria, specifically, was used and was used to intentionally introduce different DNA, in order to avoid the Leigh syndrome. This is a process that's been talked about for awhile, and was legalized in the UK for the first time last year, but hadn't actually been performed yet.

The baby and parents are all healthy and doing well, according to The Guardian, but researchers learning about the news this week had some mixed feelings. For one, the paper hasn't actually been peer-reviewed or published yet, so it's a little early to confirm the report. There are also some ethical questions still swirling around this procedure.

"With radical new treatments like this there are always challenging ethical issues," Darren Griffin, a professor of genetics at the University of Kent, said in a statement to the UK's Science Media Centre. "However, any concerns need to be balanced against the ramifications of not implementing such a technology when families are in need of it. […] The diseases to which this treatment is relevant are devastating and thus this treatment brings new hope to many families."

Other experts in the field expressed concern over the shady way this procedure took place: though the UK has a strict regulatory framework for how to conduct mitochondrial transfer, Mexico doesn't, and the fact that a US doctor was willing to meet a foreign couple in a third country in order to skirt regulation raised some eyebrows.

"It risks encouraging others to follow the example, as we saw with 'stem cell tourism'," said Dr Dusko Ilic, a stem cell scientist at King's College London, in a statement to the Science Media Centre. "That could be dangerous as understandably impatient people pursue treatment in the very places where regulation is the least strict."

Many are eager to see the first baby born through this process in the UK, where a long battle established tight controls to ensure the safety and ethics of such a procedure. Though this baby is definitely a first of sorts, the headlines splashed around websites Tuesday really ought to have an asterisk next to them. I guess the headline "First Mitochondrial Transfer to Lead to Live Birth Happened a Few Months Ago, Most Likely" just wasn't catchy enough.

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